The present invention relates to an arrangement for mixing and/or kneading of viscous, plastic, powder or grain materials.
More particularly, it relates to an arrangement which has a driveable screw shaft arranged in a tubular housing opening and composed of a shaft which transmits a torque and a plurality of screw elements arranged on the shaft one behind the other and fixedly connecting the shaft by at least one edge with a substantially rectangular cross-section. The screw shaft operates for partial load distribution, while the wedge is partially arranged on the shaft and partially in the screw element so that the longer sides of the wedge cross-section extend parallel to a tangent to the shaft periphery and its shorter sides are arranged at a right angle to the longer sides.
An arrangement of the above-mentioned type is disclosed for example in the German document DE-C-813,154. During kneading with this arrangement a maximum quantity of energy of the driven shaft is transmitted to the material to be treated in the arrangement and converted in the material into work. The wedge or the wedges between the shaft and the screw elements position the screw elements in the proper turning position on the shaft and the torque during the operation is transmitted from the shaft through the screw elements to the material to be worked.
In the known arrangement swelling torsion loading of the shaft acts only in one direction, which influences its fatigue line. For the loading capacity of the shaft, it is necessary to determine the maximum stress concentration which occurs in the wedge groove and whose maximum permissible value must not be exceeded. The wedge or the wedges are arranged so that their cross-section is radial and symmetrical substantially for each half in the shaft and in the screw elements. This however produces a groove bottom which is not optimal with respect to a notch effect and also results in a poor accessibility of the groove for testing and cleaning.